Method of stabilizing imino-functional silane

ABSTRACT

A method of stabilizing imino-functional silane involving adding thereto at least one Brønsted-Lowry base to inhibit, suppress or prevent the addition reactions of the imino-functional silane with itself to form a imino- and amino-functional silane and the subsequent deamination reactions to form conjugated carbon-carbon double bond-containing imino-functional silanes and stabilized imino-functional silanes containing the at least one Brønsted-Lowry base.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of provisional U.S. patentapplication Ser. No. 62/362,741 filed Jul. 15, 2016, the entire contentsof which are incorporated by reference herein.

FIELD OF THE INVENTION

This invention relates to imino-functional silanes and, moreparticularly, to a method of purifying and/or for the post-productiontreatment of imino-functional silanes to inhibit addition reactions onthe imino-functional silanes to produce an imino- and amino-functionalsilane and the subsequent deamination reaction to produce a conjugatedcarbon-carbon double bond containing imino-functional silane that occurstherein during storage.

BACKGROUND OF THE INVENTION

Iminosilanes of various kinds are known in the art and are known to beuseful as, among others, intermediates for the production ofamine-containing compounds and silylated polymers, adhesion promotersfor coating, adhesive and sealants and as coupling agents for mineralfilled composites.

Among the known imino-functional silanes and methods for theirpreparation are the aldimino-functional silanes, ketimino-functionalsilanes and preparative methods described in U.S. Pat. No. 2,942,019;the N,N′-bis[(tri(substituted)silylalkylene]-1,4-xylene-a,a′-diiminesand preparative methods described in U.S. Pat. No. 3,681,420; theimino-functional silanes and preparative methods utilizing isocyanatesdescribed in U.S. Pat. No. 5,134,234; the aldimino-functional silanesand ketimino-functional silanes and preparative methods described inU.S. Pat. No. 5,739,201; the imino-functional silanes and amine exchangepreparative methods described in U.S. Pat. Nos. 6,586,612 and 6,998,449;the aldimino-functional silanes and preparative methods described inU.S. Pat. Nos. 7,906,673 and 8,877,955; the ketimino-functional silanesand preparative methods described in U.S. Pat. No. 7,923,572; and, theamino-functional silanes (“activated silanes”) and preparative methodsdescribed in WO2009/043599. The contents of each of these patentpublications are incorporated herein in their entirety.

Imino-functional silanes undergo addition reactions to form imido- andamino-functional silanes and these imido- and amino-functional silanesmay further undergo deamination reactions to form conjugatedcarbon-carbon double bond containing imino-functional silanes. Theseundesirable reaction products reduce the content of the desiredimino-functional silanes, may generate color making them unsuitable asintermediates or adhesion promoters for clear compositions and curtailtheir storage stability. Because of these adverse effects on productpurity and storage stability, a need has arisen for a method ofinhibiting, suppressing or preventing the reactions of imino-functionalsilanes with themselves and the subsequent deamination reactions.

SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided a method ofstabilizing imino-functional silane comprising:

a) adding a Brønsted-Lowry base to an imino-functional silane; and,

b) mixing the imino-functional silane with the at least oneBrønsted-Lowry base to provide stabilized imino-functional silane.

Although not intended to be bound by theory, it is believed that theuntreated imino-functional silane contains at least one acidic protonsource and in the presence thereof and increasingly over time, theimino-functional silane undergoes reaction with itself to formundesirable and unwanted addition and deamination reactions. Thereactants used in the process for preparing the imino-functional silane,such as aldehydes, ketones and/or aminosilanes, may contain a source ofprotons (H+), e.g., a Brønsted-Lowry acid. Even in trace amounts, theseBrønsted-Lowry acids can catalyze the aforementioned undesirableimino-functional silane addition and deamination reactions therebygenerating as a reaction product, a conjugated carbon-carbon double bondcontaining imino-functional silane and as by-product, theamino-functional silane that was originally employed as reactant in thepreparation of the desired imino-functional silane. Such undesirablereactions reduce the amount of desired imino-functional silane overtime, e.g., during storage, and can result in a significant loss ofimino-functional silane product accompanied by a wasteful buildup ofconjugated carbon-carbon double bond containing imino-functional silaneand amino-functional silane impurities.

The method of the invention when applied to freshly prepared iminosilaneproduct effectively inhibits or prevents addition and deaminationreactions of the iminosilane from occurring, or if some addition anddeamination reactions have already taken place, prevents such reactionsfrom proceeding further. In one embodiment, the method of the inventiontherefore preserves, or substantially preserves, the original content ofdesired imino-functional silane product, suppresses or eliminates thegeneration of wasteful addition and deamination reaction products andgreatly increases the storage stability of the treated imino-functionalsilane product.

DETAILED DESCRIPTION OF THE INVENTION

In the specification and claims herein, the following terms andexpression are to be understood as having the hereinafter indicatedmeanings.

The singular forms “a,” “an” and “the” include the plural, and referenceto a particular numerical value includes at least that particular valueunless the context clearly dictates otherwise.

All methods described herein may be performed in any suitable orderunless otherwise indicated herein or otherwise clearly contradicted bycontext. The use of any and all examples or exemplary language (e.g.,“such as”) provided herein is intended merely to better illuminate theinvention and does not pose a limitation on the scope of the inventionunless otherwise claimed.

No language in the specification should be construed as indicating anynon-claimed element as essential to the practice of the invention.

As used herein, the terms “comprising,” “including,” “containing,”“characterized by” and grammatical equivalents thereof are inclusive oropen-ended terms that do not exclude additional, unrecited elements ormethod steps, but will also be understood to include the morerestrictive terms “consisting of” and “consisting essentially of.”

Composition percentages are given in weight percent unless otherwiseindicated.

It will be understood that any numerical range recited herein includesall sub-ranges within that range and any combination of the variousendpoints of such ranges or sub-ranges.

It will be further understood that any compound, material or substancewhich is expressly or implicitly disclosed in the specification and/orrecited in a claim as belonging to a group of structurally,compositionally and/or functionally related compounds, materials orsubstances includes individual representatives of the group and allcombinations thereof.

The expression, “proton source”, means a compound that can release aproton.

The expression “Brønsted-Lowry acid” shall be understood herein to applyto any compound that can transfer a proton to any other compound, i.e.,to a proton donor. A proton is a nuclear particle with a unit positiveelectrical charge; it is represented by the symbol H⁺ as it constitutesthe nucleus of a hydrogen atom.

The expression “Brønsted-Lowry base” shall be understood herein to applyto any compound that accepts a proton, i.e., to a proton acceptor.

The expression “conjugated carbon-carbon double bond containingimino-functional silane” shall be understood herein to mean any moleculecontaining the bond sequence C═C—C═N where C═C denotes a carbon-carbondouble bond and C═N denotes a carbon-nitrogen double bond, i.e., animino group.

The term “hydrocarbon group” means any hydrocarbon compound containingonly hydrogen and carbon atoms from which one or more hydrogen atoms hasbeen removed. Hydrocarbon group is inclusive of alkyl, alkenyl, alkynyl,alkylene, cycloalkyl, cycloalkenyl, cycloalkynyl, aryl, aralkyl andarenyl.

A “heterocarbon group” means a hydrocarbon group containing one or moreheteroatoms.

The term “heteroatom” means any of the Group 13-17 elements exceptcarbon and includes, for example, oxygen, nitrogen, silicon, sulfur,phosphorus, fluorine, chlorine, bromine and iodine.

The term “alkyl” means any monovalent, saturated straight chain orbranched chain hydrocarbon group; the term “alkenyl” means anymonovalent straight chain or branched chain hydrocarbon group containingone or more carbon-carbon double bonds where the site of attachment ofthe group can be either at a carbon-carbon double bond or elsewheretherein; and, the term “alkynyl” means any monovalent straight chain orbranched chain hydrocarbon group containing one or more carbon-carbontriple bonds and, optionally, one or more carbon-carbon double bonds,where the site of attachment of the group can be either at acarbon-carbon triple bond, a carbon-carbon double bond or elsewheretherein.

Representative examples of alkyls include methyl, ethyl, propyl andisobutyl. Examples of alkenyls include vinyl, propenyl, allyl,methallyl, ethylidenyl norbornane, ethylidene norbornyl, ethylidenylnorbornene and ethylidene norbornenyl. Examples of alkynyls includeacetylenyl, propargyl and methylacetylenyl.

The term “cycloalkyl” means any monovalent cyclic aliphatic hydrocarbongroup; the term “cycloalkenyl” means any monovalent cyclic aliphatichydrocarbon group containing one or more carbon-carbon double bondswhere the site of attachment of the group can be either at acarbon-carbon double bond or elsewhere therein; and, the term“cycloalkynyl” means any monovalent cyclic aliphatic hydrocarbon groupcontaining one or more carbon-carbon triple bonds and, optionally, oneor more carbon-carbon double bonds, where the site of attachment of thegroup can be either at a carbon-carbon triple bond, a carbon-carbondouble bond or elsewhere therein.

Representative examples of cycloalkyl include cyclopentyl, cyclobutyl,cyclopentyl, cycloheptyl, cyclooctyl. Examples of cyloalkenyl includecyclopentenyl, cycloheptenyl and cyclooctatrienyl. An example ofcycloalkynyl is cycloheptynyl.

The terms “cycloalkyl”, “cycloalkenyl”, and “cycloalkynyl” includebicyclic, tricyclic and higher cyclic structures as well as theaforementioned cyclic structures further substituted with alkyl,alkenyl, and/or alkynyl groups. Representative examples includenorbornyl, norbornenyl, ethylnorbornyl, ethylnorbornenyl, cyclohexyl,ethylcyclohexyl, ethylcyclohexenyl, cyclohexylcyclohexyl andcyclododecatrienyl.

The term “aryl” means any monovalent aromatic hydrocarbon group; theterm “aralkyl” means any alkyl group (as defined herein) in which one ormore hydrogen atoms have been substituted by the same number of likeand/or different aryl (as defined herein) groups; and, the term “arenyl”means any aryl group (as defined herein) in which one or more hydrogenatoms have been substituted by the same number of like and/or differentalkyl groups (as defined herein). Examples of aryls include phenyl andnaphthalenyl. Examples of aralkyls include benzyl and phenethyl.Examples of arenyls include tolyl and xylyl.

Other than in the working examples, or where otherwise indicated, allnumbers expressing amounts of materials, reaction conditions, timedurations, quantified properties of materials, and so forth, stated inthe specification and claims are to be understood as being modified inall instances by the term “about”.

Useful hydrocarbyl groups include alkyl groups examples of which aremethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl,n-pentyl, isopentyl, neopentyl and tert-pentyl; hexyl such as n-hexyl;heptyl such as n-heptyl; octyl such as n-octyl, isooctyl and2,2,4-trimethylpentyl; nonyl such as n-nonyl; decyl such as n-decyl; andcycloalkyl, such as cyclopentyl, cyclohexyl, cycloheptyl andmethylcyclohexyl. Examples of alkenyl groups include vinyl, propenyl,allyl and methallyl. Examples of cylcoalkenyl groups includecyclohexenyl, norbornenyl, ethylnorbornenyl, ethylidenyl norbornane,ethylidene norbornyl, ethylidenylnorbornene and ethylidene norbornenyl.Examples of alkynyl groups include acetylenyl, propargyl andmethylacetylenyl. Examples of aryl groups include phenyl, naphthyl; o-,and p-tolyl, xylyl, ethylphenyl and benzyl.

Among the more common known methods of producing imino-functionalsilanes are those involving the condensation reaction ofamino-functional silane and a carbonyl compound, i.e., an aldehydeand/or ketone, either of which may contain additional functionality suchas a secondary amino, hydroxyl or sulfhydryl group. The reaction splitsout water which is advantageously collected as it forms. Upon completionof the reaction, excess reactant(s) are removed advantageously from theproduct imino-functional silane, for example, by distillation undervacuum. These reactions may be catalyzed by acids and/or bases.

Other methods of producing imino-functional silanes are those involvingthe reactions of imino-functional compounds that do not contain a silylgroup with amino-functional silanes. The reactions produceimino-functional silanes and the byproduct amines, which do not containa silyl group. These reactions may be catalyzed by acids and/or bases.

In one embodiment of the present invention, the imino-functional silaneto be treated is an imino-functional silane of general formula (I):

wherein:

R⁰ is hydrogen, a monovalent hydrocarbon group of from 1 to about 20carbon atoms such as an alkyl, cycloalkyl, aryl, alkaryl or aralkyl,group containing up to about 20 carbon atoms, or a monovalentheterocarbon group of from 1 to about 20 carbon atoms containing one ormore heteroatoms such as N, O and/or S, specifically a hydrogen, astraight chain alkyl group of from 1 to about 10 carbon atoms, morespecifically from 2 to 4 carbon atoms, e.g., ethyl, propyl or butyl, ora branched alkyl group of from 3 to about 10 carbon atoms, morespecifically from 3 to about 6 carbon atoms and still more specifically3 or 4 carbon atoms, e.g., isopropyl or isobutyl;

R¹ is a divalent hydrocarbon group of from 1 to about 20 carbon atomssuch as alkylene, cycloalkylene, arylene, alkarylene or aralkylene,group containing up to about 20 carbon atoms or a divalent heterocarbongroup of from 1 to about 20 carbon atoms containing one or moreheteroatoms such as N, O and/or S, specifically a straight chainalkylene group of from 1 to about 10 carbon atoms, more specifically 2to about 4 carbon atoms, e.g., ethylene, propylene or butylene, or abranched chain alkylene group of from 2 to about 10 carbon atoms, morespecifically from 2 to about 6 carbon atoms and still more specifically3 or 4 carbon atoms, e.g., isopropylene or isobutylene;

R² is an alkyl group of from 1 to about 5 carbon atoms, e.g., methyl,ethyl, propyl, isopropyl, butyl, isobutyl, pentyl or isopentyl;

R³ is phenyl or an alkyl group of from 1 to about 8 carbon atoms,specifically methyl or ethyl;

G is a monovalent or polyvalent hydrocarbon group of from 1 to about 30carbon atoms or a heterocarbon group of from I to about 30 carbon atomscontaining one or more heteroatoms such as N, O and/or S, specifically astraight chain alkyl group of from 1 to about 10 carbon atoms, morespecifically from 2 to 4 carbon atoms, e.g., ethyl, propyl or butyl, asubstituted alkyl group containing from 1 to about 10 carbon atoms andone or more heteroatoms such as N, O and/or S, a branched chain alkylgroup of from 3 to about 10 carbon atoms, more specifically from 3 toabout 6 carbon atoms and still more specifically 3 or 4 carbon atoms, asubstituted branched alkyl group of from 3 to about 10 carbon atomscontaining one or more heteroatoms such as N, O and/or S, a cycloalkylgroup of from 3 to about 10 carbon atoms, more specifically from about 5to about 8 carbon atoms, e.g. cyclopentyl, cyclohexyl, cycloheptyl orcyclooctyl, an aryl group of from about 6 to about 10 carbon atoms, anarenyl group of from about 7 to about 10 carbon atoms, an aralkyl groupof from about 7 to about 10 carbon atoms, a straight chain alkylenegroup of from 1 to about 10 carbon atoms, more specifically from 2 to 4carbon atoms, e.g., ethylene, propylene or butylene, or a branched chainalkylene group of from 2 to about 10 carbon atoms, more specificallyfrom 2 to about 6 carbon atoms and still more specifically 3 or 4 carbonatoms, a cycloalkylene group of from 3 to about 10 carbon atoms, morespecifically from about 5 to about 8 carbon atoms, e.g., cyclopentylene,cyclohexylene, cycloheptylene or cyclooctylene, an arylene group of fromabout 6 to about 10 carbon atoms, an arenylene group of from about 7 toabout 10 carbon atoms or an aralkylene group of from about 7 to about 10carbon atoms;

subscript a is 0, 1 or 2, specifically 1; and,

subscript x is 1, 2, 3 or 4, specifically 1 or 2 and more specifically1.

Imino-functional silane (I) can be obtained by the reaction in a knownmanner, e.g., as described in U.S. Pat. No. 7,906,673, the entirecontents of which are incorporated by reference herein, ofamino-functional silane of general formula (II):

in which R¹, R² and R³ and subscript a have the aforestated meanings,with a carbonyl-containing compound of general formula (III):

in which G, R⁰ and subscript x have the aforestated meanings, theproduct imino-functional silane (I) being recovered employing anyconventional or otherwise known technique(s), e.g., such as thosedescribed in aforementioned U.S. Pat. No. 7,906,673.

In another embodiment of the present invention, the imino-functionalsilane to be treated is an aldimino-functional silane of general formula(IV):

wherein:

R¹ is a divalent hydrocarbon group of up to about 20 carbon atoms or adivalent heterocarbon group of up to about 20 carbon atoms containingone or more heteroatoms such as N, O and/or S, specifically a straightchain alkylene group of from 1 to about 10 carbon atoms, morespecifically from 2 to 4 carbon atoms, e.g., ethylene, propylene orbutylene, or a branched chain alkylene group of from 2 to about 10carbon atoms, more specifically from 2 to about 6 carbon atoms and stillmore specifically 3 or 4 carbon atoms, e.g., isopropylene orisobutylene;

R² is an alkyl group of from 1 to about 5 carbon atoms, e.g., methyl,ethyl, propyl, isopropyl, butyl, isobutyl, pentyl or isopentyl;

R³ is phenyl or an alkyl group of from 1 to about 8 carbon atoms,specifically methyl or ethyl;

Y¹ and Y² each independently is hydrogen, an organic radical or togetherwith the carbon atom to which they are bonded form a carbocyclic orheterocyclic ring of from about 5 to about 8, and specifically, 6, ringatoms;

Y³ is a hydrogen, an unsubstituted or substituted alkyl group containingone or more heteroatoms such as N, O and/or S, an unbranched or branchedalkyl or alkylenyl group of up to about 10 carbon atoms, a substitutedor unsubstituted aryl or arylalkyl group of up to about 20 carbon atoms,specifically from about 6 to about 12 carbon atoms and still morespecifically from about 6 to about 8 carbon atoms, or an —OR⁴,—OC(═O)—R⁴, —C(═O)OR⁴ or —C(═O)R⁴ group in which R⁴ is an unsubstitutedor substituted alkyl group of from 3 to about 20 carbon atoms,specifically from 3 to about 10 carbon atoms and more specifically from3 to about 6 carbon atoms, or an unsubstituted or substituted aryl oraralkyl group of up to about 20 carbon atoms, specifically from about 6to about 12 carbon atoms and still more specifically from about 6 toabout 8 carbon atoms; and,

subscript a is 0, 1 or 2

Aldimino-functional silane (W) can be obtained by the reaction in aknown manner, e.g., as described in aforementioned U.S. Pat. No.7,906,673, of amino-functional silane of general formula (II):

in which R¹, R² and R³ and subscript a have the aforestated meanings,with aldehyde of general formula (V):

in which Y¹, Y² and Y³ have the aforestated meanings, the productaldimino-functional silane (V) being recovered employing anyconventional or otherwise known technique(s), e.g., such as thosedescribed in aforementioned U.S. Pat. No. 7,906,673.

In yet another embodiment of the present invention, the imino-functionalsilane to be treated is an aldimino-functional silane of general formula(VI):

wherein:

R¹, R², R³ and subscript a have the aforestated meanings foraldimino-functional silane (IV);

R⁵ and R⁶ each independently is hydrogen, a monovalent hydrocarbon groupof from 1 to about 12 carbon atoms or together with the carbon atom towhich they are bonded form an unsubstituted or substituted ring of fromabout 5 to about 12 carbon atoms, specifically from about 5 to about 8carbon atoms and more specifically, 5 or 6 carbon atoms, or aheterocarbon group containing from 1 to about 12 carbon atoms and one ormore heteroatoms such as N, O and/or S;

R⁷ is hydrogen, a monovalent hydrocarbon group such as an alkyl,cycloalkyl, aryl, alkaryl or aralkyl group of up to about 20 carbonatoms, more specifically up to about 12 carbon atoms and morespecifically up to about 6 carbon atoms, a heterocarbon group containingup to about 20 carbon atoms and one or more heteroatoms such as N, Oand/or S, or an alkoxycarboxyl group of from 2 to about 20 carbon atoms,specifically from 2 to about 12 carbon atoms and more specifically from2 to about 6 carbon atoms; and,

R⁸ and R⁹ each independently is a monovalent hydrocarbon group such asan alkyl, cycloalkyl, aryl, alkaryl or aralkyl group of up to about 20carbon atoms, more specifically up to about 12 carbon atoms and morespecifically up to about 6 carbon atoms, a heterocarbon group containingup to about 20 carbon atoms and one or more heteroatoms such as N, Oand/or S, or an alkoxycarboxyl group of from 2 to about 20 carbon atoms,specifically from 2 to about 12 carbon atoms and more specifically from2 to about 6 carbon atoms, or R⁸ and R⁹ and the carbon atom to whichthey are bonded form an unsubstituted or substituted ring of from about5 to about 12 carbon atoms containing zero, one or more heteroatoms suchas N, O and/or S.

Aldimino-functional silane (VI) can be obtained by the reaction in aknown manner, e.g., as described in U.S. Pat. No. 8,877,955, the entirecontents of which are incorporated by reference herein, of aminosilane(II), supra, as described above with aldehyde of general formula (VII):

in which R⁵, R⁶, R⁷, R⁸ and R⁹ have the aforestated meanings of thealdimino-functional silane (VI), the product aldimino-functional silane(VI) being recovered employing any conventional or otherwise knowntechnique(s), e.g., such as those described in aforementioned U.S. Pat.No. 8,877,955.

In yet another embodiment of the present invention, the imino-functionalsilane to be stabilized by the method of the invention is aketimino-functional silane of general formula (VIII):

wherein:

R¹, R², R³ and subscript a each have one of the same meanings statedabove for aldimino-functional silane (IV);

R¹⁰ and R¹¹ each independently is a monovalent hydrocarbon group of upto about 20 carbon atoms, specifically up to about 12 carbon atoms andstill more specifically up to about 6 carbon atoms, or a monovalentheterocarbon group of up to about 20 carbon atoms, specifically up toabout 12 carbon atoms and still more specifically up to about 6 carbonatoms, containing one or more heteroatoms such as N, O and/or S; and,

subscript a is 0, 1 or 2.

Ketimino-functional silane (VIII) can be obtained by the reaction in aknown manner, e.g., as described in U.S. Pat. No. 7,923,572, the entirecontents of which are incorporated by reference herein, ofamino-functional silane (II), supra, as described above with a ketone ofgeneral formula (IX):

in which R¹⁰ and R¹¹ have the aforestated meanings, the productketimino-functional silane (VIII) being recovered employing anyconventional or otherwise known technique(s), e.g., such as thosedescribed in aforementioned U.S. Pat. No. 7,923,572.

Representative and non-limiting examples of amino-functional silanes(II) that can be used to prepare imino-functional silane (I),aldimino-functional silanes (IV) and (VI) and ketimino-functional silane(VIII) include 3-aminopropyltrimethoxysilane,3-aminopropyldimethoxymethylsilane,3-amino-2-methylpropyltrimethoxysilane, 4-aminobutyltrimethoxysilane,4-aminobutyldimethoxymethylsilane,4-amino-3-methylbutyltrimethoxysilane,4-amino-3,3-dimethylbutyltrimethoxysilane,4-amino-3,3-dimethylbutyldimethoxymetyylsilane,2-aminoethyltrimethoxysilane, 2-aminoethyldimethoxymethylsilane,aminomethyltrimethoxysilane, aminomethyldimethoxymethylsilane,aminomethylmethoxydimethylsilane,7-amino-4-oxaheptyldimethoxymethylsilane as well as their analogspossessing ethoxy, propoxy or isopropoxy groups on the silicon atom;so-called diaminosilanes which in addition to a primary amino grouppossess a secondary amino group (—NH group) which, for example, is inthe gamma position relative to the silicon atom, for example,N-(2-aminoethyl)-3-aminopropyltrimethoxysilane,N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane,N-(2-aminoethyl)-3-aminopropyltriethoxysilane andN-(2-aminoethyl)-3-aminopropyltriisopropoxysilane; and so-calledtriaminosilanes, which carry besides a primary amino group, twosecondary amino groups (—NH groups) such asN-(2-aminoethyl)-N′[3-(trimethoxysily)propyl]ethylenediamine.

Representative and non-limiting examples of carbonyl compounds (III)that can be used to prepare imino-functional silane (I) includeformaldehyde, acetaldehyde, propionaldehyde, butyraldehyde,isobutyraldehyde, 2-methylbutyraldehyde, 2-ethylbutyraldehyde,2-methylvaleraldehyde, 2-ethylcapronaldehyde,cyclopentanecarboxaldehyde, cyclohexanecarboxaldehyde,1,2,3,6-tetrahydrobenzaldehyde, phenylacetaldehyde,2-methyl-3-phenylpropionaldehyde, 2-phenylpropionaldehyde, anddiphenylacetaldehyde, 2,2-dimethyl-3-methylaminopropanal,2,2-dimethyl-3-dimethylaminopropanal, 2,2-dimethyl-3-ethylaminopropanal,2,2-dimethyl-3-diethylaminopropanal,2,2-dimethyl-3-bis(2-methoxyethyl)aminopropanal,2,2-dimethyl-3-butylaminopropanal, 2,2-dimethyl-3-dibutylaminopropanal,2,2-dimethyl-3-hexylaminopropanal,2,2-dimethyl-3-(2-ethylhexyl)aminopropanal,2,2-dimethyl-3-dodecylaminopropanal,2,2-dimethyl-3-(N-pyrrolidino)propanal,2,2-dimethyl-3-(N-piperidino)propanal,2,2-dimethyl-3-(N-morpholino)propanal,2,2-dimethyl-3-(N-(2,6-dimethyl)morpholino)propanal,2,2-dimethyl-3-benzylaminopropanal,2,2-dimethyl-3-(N-benzylmethylamino)propanal,2,2-dimethyl-3-(N-benzylisopropylamino)propanal,2,2-dimethyl-3-cyclohexylaminopropanal and2,2-dimethyl-3-(N-cyclohexylmethylamino)propanal, 4-oxo-pentanal,acetone, methylethylketone, methylpropylketone, methylisopropylketone,methylisobutylketone, dimethylketone, diethyl ketone, dipropylketone,diisopropylketone, dibutylketone and diisobutylketone, cyclopentanone,triemethylcyclopentanone, cyclohexanone, trimethylcyclohexanone,6-oxo-2-heptanone, 5-oxo-2-hexanone, 1,4-diacetylbenzene,1,3,5-triacetylbenzene and acetylacetone.

Representative and non-limiting examples of aldehydes (V) that can beused to prepare aldimino-functional silane (VI) include ethers ofbeta-hydroxyaldehydes as formed from a crossed aldol reaction fromformaldehyde and a second aldehyde such as 2-methylbutyraldehyde,2-ethyl-butyraldehyde, 2-methylvaleraldehyde, 2-ethylcaproaldehyde,cyclopentane-carboxaldehyde, cyclohexanecarboxaldehyde,1,2,3,6-tetrahydrobenz-aldehyde, 2-methyl-3-phenylpropionaldehyde,2-phenylpropionaldehyde (hydratropaldehyde), and diphenylacetaldehyde,and alcohols such as methanol, ethanol, propanol, isopropanol, butanol,2-ethylhexanol or fatty alcohols, such as, for example, 3-methoxy- and3-ethoxy- and 3-propoxy- and 3-isopropoxy- and 3-butoxy-, and also3-(2-ethylhexoxy)-2,2-dimethylpropanal; products of an esterification ofthe aforementioned β-hydroxyaldehydes such as 3-hydroxy-pivalaldehyde,3-hydroxyisobutyraldehyde, 3-hydroxypropionaldehyde,3-hydroxybutyraldehyde, 3-hydroxyvaleraldehyde,2-hydroxymethyl-2-methyl-butyraldehyde,2-hydroxymethyl-2-ethylbutyraldehyde,2-hydroxymethyl-2-methylvaleraldehyde, 2-hydroxymethyl-2-ethylhexanal,1-hydroxymethyl-cyclopentanecarbaldehyde,1-hydroxymethylcyclohexanecarbaldehyde,1-hydroxymethylcyclohex-3-enecarbaldehyde,2-hydroxymethyl-2-methyl-3-phenylpropionaldehyde,3-hydroxy-2-methyl-2-phenylpropionaldehyde and3-hydroxy-2,2-diphenylpropionaldehyde with carboxylic acids such asformic acid, acetic acid, propionic acid, butyric acid, isobutyric acid,2-ethylcaproic acid, and benzoic acid; and, esterification products ofthe aforementioned beta-hydroxyaldehydes such as3-hydroxy-pivalaldehyde, 3-hydroxyisobutyraldehyde, 3-hydroxypropanal,3-hydroxy-butyraldehyde, 3-hydroxyvaleraldehyde,2-hydroxymethyl-2-methyl-butyraldehyde,2-hydroxymethyl-2-ethylbutyraldehyde,2-hydroxymethyl-2-methylvaleraldehyde, 2-hydroxymethyl-2-ethylhexanal,1-hydroxymethyl-cyclopentanecarbaldehyde,1-hydroxymethylcyclohexanecarbaldehyde,1-hydroxymethylcyclohex-3-enecarbaldehyde,2-hydroxymethyl-2-methyl-3-phenylpropionaldehyde,3-hydroxy-2-methyl-2-phenylpropionaldehyde, and3-hydroxy-2,2-diphenylpropionaldehyde with carboxylic acids such as, forexample, lauric acid, tridecanoic acid, myristic acid, pentadecanoicacid, palmitic acid, margaric acid, stearic acid, nonadecanoic acid,arachidic acid, palmitoleic acid, oleic acid, erucic acid, linoleicacid, linolenic acid, eleostearic acid, arachidonic acid, succinic acid,glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid,sebacic acid, 1,12-dodecanedioic acid, maleic acid, fumaric acid,hexahydrophthalic acid, hexahydroisophthalic acid,hexahydro-terephthalic acid, 3,6,9-trioxaundecanedioic acid, and similarderivatives of polyethylene glycol, dehydrogenated ricinoleic acids, andalso fatty acids from the industrial saponification of natural oils andfats such as, for example, rapeseed oil, sunflower oil, linseed oil,olive oil, coconut oil, oil-palm kernel oil, and oil-palm oil.

Representative and non-limiting examples of aldehydes (VII) that can beused to prepare aldimino-functional silane (VI) include2,2-dimethyl-3-methylaminopropanal,2,2-dimethyl-3-dimethylaminopropanal, 2,2-dimethyl-3-ethylaminopropanal,2,2-dimethyl-3-diethylaminopropanal,2,2-dimethyl-3-bis(2-methoxyethyl)aminopropanal,2,2-dimethyl-3-butylaminopropanal, 2,2-dimethyl-3-dibutylaminopropanal,2,2-dimethyl-3-hexylaminopropanal,2,2-dimethyl-3-(2-ethylhexyl)aminopropanal,2,2-dimethyl-3-dodecylaminopropanal,2,2-dimethyl-3-(N-pyrrolidino)propanal,2,2-dimethyl-3-(N-piperidino)propanal,2,2-dimethyl-3-(N-morpholino)propanal,2,2-dimethyl-3-(N-(2,6-dimethyl)morpholino)propanal,2,2-dimethyl-3-benzylaminopropanal,2,2-dimethyl-3-(N-benzylmethylamino)propanal,2,2-dimethyl-3-(N-benzylisopropylamino)propanal,2,2-dimethyl-3-cyclohexylaminopropanal and2,2-dimethyl-3-(N-cyclohexylmethylamino)propanal.

Representative and non-limiting examples of ketones (IX) that can beused to prepare ketiminosilanes (VIII) include aliphatic ketones such asacetone, methylethylketone, methylpropylketone, methylisopropylketone,methylisobutylketone, dimethylketone, diethyl ketone, dipropylketone,diisopropylketone, dibutylketone and diisobutylketone, and cyclicketones such as cyclopentanone, triemethylcyclopentanone, cyclohexanoneand trimethylcyclohexanone.

In one particular embodiment, the method of stabilizing imino-functionalsilane in accordance with the invention comprises:

a) adding a Brønsted-Lowry base to an imino-functional silane that issusceptible to undergoing self-addition and deamination reactionsresulting from the presence therein of a proton source; and,

b) mixing the imino-functional silane with the Brønsted-Lowry basethereby neutralizing the proton source and providing stabilizedimino-functional silane.

In the aforedescribed embodiment of the method of the invention, theBrønsted-Lowry base added to the imino-functional silane in step (a)should be sufficient to inhibit self-addition and deamination reactionsof the imino-functional silane. In one embodiment, such amount ofBrønsted-Lowry base will generally be at least about 1 molar equivalent,more specifically from about 1 to about 10 molar equivalents and evenmore specifically from about 1.2 to about 10 molar equivalents, based onthe moles of proton source present in the imino-functional silane.

The foregoing embodiment may additionally comprise:

c) separating the Brønsted-Lowry base from the mixture ofimino-functional silane and Brønsted-Lowry base of step (b) to provide astabilized, imino-functional silane, preferably one that issubstantially free of Brønsted-Lowry base; and,

d) collecting the stabilized imino-functional silane of step (c).

It will be appreciated that the selected Brønsted-Lowry base must besufficiently basic to neutralize the proton source. In one embodiment,the conjugate acid of the Brønsted-Lowry base use to neutralize theproton source will have a pKa in water of greater than about 12,specifically a pKa of from about 12 to about 25, and more specifically apKa of from about 13 to about 20. The pKa values for the conjugate acidof the Brønsted-Lowry base can be found in, inter alia, “AdvancedOrganic Chemistry”, 3rd ed., J. March (1985) and in references citedtherein, and in “CRC Handbook of Chemistry and Physics”, David R. Lide,editor, 72 ed. (CRC Press 1991-92). Such pKa values can also bedetermined by the method of R. G. Bates and G. D. Pinching, J. Am. Chem.Soc., 72, 1393 (1950) at 25° C. The Brønsted-Lowry base will havesufficient basicity if it is a hydroxide, alkoxide or oxide of an alkalior alkaline metal.

As used herein, the expression “substantially free of Brønsted-Lowrybase” shall be understood to mean a stabilized imino-functional silanecontaining less than about 1 weight percent, specifically less thanabout 0.01 weight percent, more specifically less than about 0.0001weight percent, and still more specifically from about 0.0001 to about0.1 weight percent, Brønsted-Lowry base based on the weight of thestabilized imino-functional silane.

In one embodiment, the amount of Brønsted-Lowry base in the stabilizedimino-functional silane may be determined using Inductively CoupledPlasma Mass Spectrometry.

In one embodiment, a stabilized imino-functional silane is animino-functional silane containing less than about 2 weight percentconjugated carbon-carbon double bond-containing imino-functional silanebased on the total weight of conjugated carbon-carbon doublebond-containing imino-functional silane and imino-functional silaneafter storage (aging) at 25° C. for 4 weeks. More specifically, astabilized imino-functional silane is an imino-functional silane thatcontains less than about 0.5 weight percent conjugated carbon-carbondouble bond-containing imino-functional silane, and still morespecifically, less than 0.1 weight percent of conjugated carbon-carbondouble bond-containing imino-functional silane, based on the totalweight of conjugated carbon-carbon double bond-containingimino-functional silane and imino-functional silane after storage at 25°C. for 4 weeks.

In another embodiment, the stabilized imino-functional silane containsless than about 15 ppm, specifically less than about 1 ppm, protonsource based on the weight of the imino-functional silane.

In one embodiment, the weight percent of the conjugated carbon-carbondouble bond-containing imino-functional silane in the stabilizedimino-functional silane can be determined employing gas chromatography(GC) using dodecane as an internal standard. In accordance with one GCprocedure, the GC column is 30 meters long and 0.25 millimeters indiameter and coated with a 0.25 micron film (HP-5 from Agilent), theflow of helium carrier gas is 1 mL per minute, with an initialtemperature profile of 50° C. for 2 minutes followed by an increase of8° C. per minute up to a temperature of 340° C., holding at the lattertemperature for 5 minutes, and using a flame ionization detector (FID).

As indicated above, even trace amounts of acidic proton will result inundesirable addition and deamination reactions of imino-functionalsilane. The proton source present in the iminosilane can come from avariety of sources, for example, as residual acid(s) associated with oneor more of the amino-functional silane, aldehyde and/or ketone reactantsand may even result from absorption of atmospheric carbon dioxide andwater by the imino-functional silane.

Neutralization of the proton source can be achieved by the addition of asuitable amount of at least one Brønsted-Lowry base to the protonsource-containing imino-functional silane. In one embodiment, a suitableamount of the at least one Brønsted-Lowry base is at least 1 molarequivalent, more specifically from about 1 to about 10 molar equivalentsand even more specifically from about 1.2 to about 10 molar equivalents,based on the moles of proton source present in the imino-functionalsilane.

In one embodiment, the Brønsted-Lowry base is a compound having thegeneral formula (X):

M(OR)_(f)   (X)

wherein M is an alkali metal or alkaline earth metal and R is hydrogen,a hydrocarbon group of from 1 to about 20 carbon atoms, a heterocarbongroup of up to about 20 carbon atoms, specifically from 1 to about 12carbon atoms and still more specifically from 1 to about 6 carbon atoms,a p-orbital of the oxygen atom containing a lone paired electrons, or M,and subscript f is 1 or 2, with the provisos that (i) when M is analkali metal, then subscript f is 1; (ii) when M is an alkaline earthmetal, then subscript f is 2, except when R is a p-orbital of oxygenatom containing a lone pair of electrons; (iii) when R is M, then M isan alkali metal; and (iv) when R is a p-orbital of the oxygen atomcontaining a lone pair of electrons, then M is an alkaline metal andsubscript f is 1. It is understood that the Brønsted-Lowry base offormula (X) is a salt of an alkali or alkaline hydroxide, alkoxide oroxide.

In another embodiment, in a preferred group of Brønsted-Lowry bases (X),M is an alkali or alkaline earth metal, R is hydrogen or a hydrocarbongroup of from 1 to about 20 carbon atoms, specifically from 1 to about12 carbon atoms, more specifically from 1 to about 6 carbon atoms, andstill more specifically methyl or ethyl, and subscript f is 1 or 2 withthe provisos that when M is an alkali metal, subscript f is 1 and when Mis an alkaline earth metal, subscript f is 2.

Representative and non-limiting examples of Brønsted-Lowry base (X) thatcan be used for this purpose include alkali metal and alkaline metalhydroxides, alkoxides and oxides such as LiOH, NaOH, KOH, CsOH, Mg(OH)₂,Ca(OH)₂, Ba(OH)₂, NaOMe, KOMe, NaOEt, KOEt, CaO, MgO, BaO and anycombinations thereof.

The amount of Brønsted-Lowry base (X) added to the imino-functionalsilane to be stabilized will generally range from about 0.0001 to about10 weight percent, specifically from about 0.001 to about 5 weightpercent, and more specifically from about 0.1 to about 1 weight percent,based upon the total weight of the imino-functional silane andBrønsted-Lowry base.

In one embodiment of the invention, the selected Brønsted-Lowry base isone that is soluble in the imino-functional silane at the concentrationemployed and matches the alkoxy functionality of the silane moiety ofthe imino-functional silane, for example, sodium methoxide in the caseof trimethoxysilane-functional iminosilane, sodium ethoxide in the caseof triethoxysilane-functional iminosilane, etc.

Neutralization of the proton source can be carried out before, during orafter distillation of the imino-functional silane reaction medium torecover any unreacted aminosilane, aldehyde and/or ketone reactant(s).However, in general, it is preferred to add the neutralizingBrønsted-Lowry base to the imino-functional silane during or immediatelyafter such distillation and more preferred, during distillation wherethe imino-functional silane is distilled from a mixture of theimino-functional silane and the Brønsted-Lowry base (X).

In embodiments of the present invention, separation of Brønsted-Lowrybase and/or Brønsted-Lowry acid can be achieved either by distillationof the treated imino-functional silane, i.e., a mixture of theimino-functional silane and Brønsted-Lowry base and/or Brønsted-Lowryacid, by extraction, by a preparatory chromatographic method, byfiltration or by any other conventional or otherwise known separationmethod, as well as by a combination of two or more of such methods.

COMPARATIVE EXAMPLE 1 Preparation of Non-Stabilized3-(1,3-Dimethylbutylidene)Aminopropyltriethoxysilane

This example is provided for comparison purposes and illustrates a knownprocess for preparing the ketiminosilane, 3-(1,3-dimethylbutylidene)aminopropyltriethoxysilane:

Into a four neck round bottom flask (5 L) fitted with a Dean Stark trapand condenser, thermocouple, addition funnel and a stopper was addedmethylisobutylketone (MIBK) (3 L). The Dean Stark trap was filled withMIBK (˜125 mL) and the head space of the reaction vessel was flushedwith nitrogen. The MIBK was heated to reflux andgamma-aminopropyltriethoxysilane (593.08 g) was added drop wise to therefluxing MIBK over a period of four hours and fifteen minutes. Theresulting reaction mixture was heated at reflux for an additional onehour after the completion of the aminosilane. Approximately 37 mL ofwater was collected in the Dean Stark trap during the course of thereaction. The reaction mixture was purified by distillation, firstremoving ˜2.2 L of volatiles (MIBK and EtOH) at atmospheric pressure.The resulting crude 3-(1,3-dimethylbutylidene)aminopropyltriethyoxysilane was further purified via vacuumdistillation.

EXAMPLE 1 Preparation of Stabilized3-(1,3-Dimethylbutylidene)Aminopropyltriethoxysilane

To a three neck round bottom flask (1 L) fitted with a Dean Stark trapand condenser, thermocouple, and addition funnel was added MIBK (585mL). The Dean Stark trap was filled with MIBK (˜25 mL) and the headspace of the reaction vessel was flushed with nitrogen. The MIBK washeated to reflux and gamma-aminopropyltriethoxysilane (100 mL) was addeddrop wise to the refluxing MIBK over a period of one hour and twentyfive minutes. The resulting reaction mixture was heated at reflux for anadditional one and a half hours after the completion of the aminosilaneaddition. Approximately 7 mL of water was collected in the Dean Starktrap during the course of the reaction. The reaction mixture waspurified by distillation, first removing ˜525 mL of volatiles (MIBK andEtOH) at atmospheric pressure. After removal of the lights, a 21 wt %solution of sodium ethoxide in ethanol (0.824 mL, 0.7156 g) was added tothe crude (3-(1,3-dimethylbutylidene) aminopropyltriethyoxysilane). Thecrude product containing sodium ethoxide was further purified via vacuumdistillation.

To demonstrate the improved storage stability of the iminosilane ofExample 1 by comparison to that of Comparative Example 1, samples ofboth products were analyzed for purity by GC over the course of sixweeks. Both materials were stored in ˜20 mL glass vials with a Teflonlined cap, the head space was purged with nitrogen and the filled vialswere stored in a dark cabinet to prevent deterioration by light. Asshown in the table below, the iminosilane made by the method of Example1 retained high purity over the course of six weeks in contrast to theproduct made by the method of Comparative Example 1 which lostapproximately 2% product after 4 weeks of aging.

TABLE I Preparative- Method As Made 1 week 2 week 4 week 6 weekComparative 98.87% No Test 97.90% 96.97% No Test Example 1 Example 199.20% 99.35% 99.47% 99.41% 99.57%

EXAMPLES 2-12 Preparation of Imino-Functional Silanes

Employing substantially the same procedures as described in Example 1,imino-functional silanes can be prepared from the amines, ketones andaldehydes and stabilized by the addition of the Brønsted-Lowry basesindicated in Table II below:

TABLE II Ex. Amine Ketone/Aldehyde Imine Product Base 2 gamma-methylisobutylketone (1,3-dimethyl-butylidene)-(3- sodiumaminopropyltriethoxysilane triethoxy-silanyl-propyl)-amine ethoxide 3gamma- methylisobutylketone (1,3-dimethyl-butylidene)-(3- sodiumaminopropyltrimethoxysilane trimethoxy-silanyl-propyl)- methoxide amine4 4-amino-3-dimethyl-1- methylisobutylketone(1,3-dimethyl-butylidene)-(2,2- sodium butyltriethoxylsilanedimethyl-4-triethoxysilanyl- ethoxide butyl)-amine 5gamma-aminopropylmethyl- acetone isopropylidene-(3-methyl- sodiumdiethoxysilane diethoxy-silanyl-propyl)-amine ethoxide 6 gamma-methylethylketone sec-butylidene-(3-triethoxy- sodiumaminopropyltriethoxysilane silanyl-propyl)-amine ethoxide 7 gamma-acetophenone [3-(triethoxy-silanyl)-propyl]- sodiumaminopropyltriethoxysilane (1-phenyl-ethylidene)-amine ethoxide 8 gamma-acetaldehyde ethylidene-(3-dimethyl-ethoxy- sodiumaminopropyldimethylethoxy- silanyl-propyl)-amine ethoxide silane 9gamma- isobutyraldehyde (3-methyl-butylidene)-(3- sodiumaminopropyltriethoxysilane triethoxy-silanyl-propyl)-amine ethoxide 10gamma- benzaldehyde benzylidene-(3-triethoxy- sodiumaminopropyltriethoxysilane silanyl-propyl)-amine ethoxide 11 gamma-3-dimethylamino-2,2- [2,2-dimethyl-3-(3-triethoxy- sodiumaminopropyltriethoxysilane dimethyl- silanyl-propylimino)-propyl]-ethoxide propionaldehyde dimethyl-amine 12 N-(2-aminoethyl)-3-methylethylketone N-sec-butylidene-N’-(3- CaOaminopropyltrimethoxysilane trimethoxy-silanyl-propyl)-ethane-1,2-diamine

EXAMPLE 13 Two-Step Process for Preparing Crude3-(1,3-Dimethylbutylidene)Aminopropyltriethyoxysilane

Into a four neck round bottom flask (1 L) fitted with a Dean Stark trap,condenser, thermocouple, addition funnel and mechanical stirrer wasadded methyl isobutyl ketone (502 grams, 5 moles). N-butylamine (73.14grams, 1 mole) was charged into the addition funnel. The reactionmixture was heated to reflux and N-butylamine was added drop wise to therefluxing methyl isobutyl ketone over a period of one hour and tenminutes. The resulting reaction mixture was heated at reflux for anadditional one hour and ten minutes after the completion of theN-butylamine addition. Approximately 18 mL of water was collected in theDean Stark trap during the course of the reaction. The Dean Stark trapand condenser were replaced with a 3″ vigreux column and distillationhead. Approximately 382 grams of volatiles, which were methyl isobutylketone and N-butylamine, were removed by vacuum stripping at a reducedpressed ranging from 280 to 420 mm Hg. After removal of the lights, anequal molar quantity of gamma-aminopropyltriethoxysilane was chargedinto the reaction mixture. N-butylamine was removed by vacuum at 55° C.and 140 mm Hg and the crude 3-(1,3-dimethylbutylidene)aminopropyltriethyoxysilane was filtered thru a 1 micron filter pad.

The crude 3-(1,3-dimethylbutylidene) aminopropyltriethyoxysilane can betreated with a Brønsted-Lowry base during the distillation process.

EXAMPLE 14 Two-Step Process for Preparing Crude Aldimino Adduct ofTerephthalaldehyde and 3-Aminopropyltriethyoxysilane

Into a four neck round bottom flask (5 L) fitted with a Dean Stark trap,condenser, thermocouple, addition funnel and mechanical stirrer wasadded terephthalaldehyde (569 grams 4.24 moles) along with toluene(2,020 grams, 22 moles). N-butylamine (620 grams, 8.48 moles) wascharged into the addition funnel. The reaction mixture was heated toreflux and N-butylamine was added drop wise to the refluxing mixtureover 3 hour and forty-five minutes. Approximately 150 ml of water wascollected during the course of the reaction. The Dean Stark trap andcondenser were replaced with a vacuum distillation head. Approximately1,777 grams of volatiles consisting of toluene and N-butylamine wereremoved by vacuum stripping at reduced pressures ranging from 18 to 150mm Hg.

After removal of the lights, 3-aminopropyltriethoxysilane (2,061.5grams, 9.33 moles) was charged into the reaction mixture. N-butylamineand excess 3-aminopropyltriethoxysilane were removed under reducedpressures ranging from 240 to 11 mm Hg with a reaction pot temperaturebetween room temperature and 170° C. The crude aldiminosilane adduct wasfiltered thru a 1 micron filter pad.

The crude aldiminosilane adduct can be treated with a Brønsted-Lowrybase during the distillation process.

EXAMPLE 15 Distillation of3-(1,3-Dimethylbutylidene)Aminopropyltriethyoxysilane from PotassiumHydroxide

Potassium hydroxide (0.1 gram) was added to 100 grams of3-(1,3-dimethylbutylidene) aminopropyltriethoxysilane prepared inaccordance with Comparative Example I. The mixture was purified viavacuum distillation at 108° C. at 1.57 mm Hg to yield a clear colorlesssolution. The purity of the product was 99.61 percent using GC. Afteraging for 14 days at 50° C., the purity of the aged product was 99.52percent. The experiment illustrated that the product can be successfullydistilled from potassium hydroxide.

EXAMPLE 16 Distillation of3-(1,3-Dimethylbutylidene)Aminopropyltriethyoxysilane from CalciumHydroxide

Calcium hydroxide (0.11 gram) was added to 106.2 grams of3-(1,3-dimethylbutylidene) aminopropyltriethoxysilane prepared inaccordance with Comparative Example I. The mixture was purified viavacuum distillation at a temperature of 124° C. and pressure of 2.4 mmHg to yield a clear colorless solution. The purity of the product was99.34 percent using GC. The experiment illustrated that the product canbe successfully distilled from calcium hydroxide.

EXAMPLE 17 Distillation of3-(1,3-Dimethylbutylidene)Aminopropyltriethyoxysilane from MagnesiumOxide

Magnesium oxide (0.10 gram) was added to 100 grams of3-(1,3-dimethylbutylidene) aminopropyltriethoxysilane prepared inaccordance with Comparative Example I. The mixture was purified viavacuum distillation at a temperature of 120° C. and pressure of 1.73 mmHg to yield a clear colorless solution. The purity of the product was99.57 percent using GC. The experiment illustrated that the product canbe successfully distilled from calcium hydroxide.

EXAMPLE 18 Distillation of3-(1,3-Dimethylbutylidene)Aminopropyltriethyoxysilane from SodiumCarbonate

Sodium carbonate (anhydrous) (0.1 grams) was added to 100 grams of3-(1,3-dimethylbutylidene) aminopropyltriethoxysilane prepared inaccordance with Comparative Example I. The mixture was purified viavacuum distillation at a temperature of 107° C. and a pressure of 1.52mm Hg to yield a clear colorless solution. The purity of the product was99.71 percent using GC. This example illustrates that the product can besuccessfully distilled from sodium carbonate.

EXAMPLE 19 Preparation 3-(1-Octylidene)Aminopropyltrimethyoxysilane

The imino-functional silane

was prepared as follows:

Into a four neck round bottom flask (2 L) fitted with a Dean Stark trap,condenser, thermocouple, addition funnel and mechanical stirrer wasadded octanal (96 grams, 0.75 mole) and toluene (800 grams, 8.68 moles).3-Aminopropyltrimethoxysilane (169 grams, 0.94 mole) was charged intothe addition funnel. The reaction mixture was heated to reflux and3-aminopropyltrimethoxysilane was added drop wise to the refluxingtoluene/octanal mixture over a period of two hour and twenty minutes.Approximately 16 mL of water was collected in the Dean Stark trap duringthe course of the reaction. The Dean Stark trap and condenser werereplaced with a short path distillation head. Approximately 780 grams ofvolatiles, which included toluene and methanol, were removed bydistillation at atmospheric pressure followed by vacuum stripping at 350to 11 mm Hg). After removal of the lights, 1.1 grams of 25 wt % solutionof sodium methoxide in methanol was added to 220 grams of crude3-(1-octylidene) aminopropyltrimethyoxysilane and further purified viavacuum distillation at a temperature range of 126 to 141° C. and at apressure of 1.45 mm Hg to yield a clear colorless solution.

While the above description contains many specifics, these specificsshould not be construed as limitations of the invention, but merely asexemplifications of preferred embodiments thereof. Those skilled in theart will envision many other embodiments within the scope and spirit ofthe invention as defined by the claims appended thereto.

1. A method of stabilizing imino-functional silane comprising: a) adding a Brønsted-Lowry base to an imino-functional silane; and, b) mixing the imino-functional silane with the Brønsted-Lowry base to provide stabilized imino-functional silane.
 2. The method of claim 1, wherein the imino-functional silane is an imino-functional alkoxysilane of general formula (I):

wherein: R⁰ is hydrogen, a monovalent hydrocarbon group of from 1 to about 20 carbon atoms or a monovalent heterocarbon group of from 1 to about 20 carbon atoms containing one or more heteroatoms; R¹ is a divalent hydrocarbon group of from 1 to about 20 carbon atoms or a divalent heterocarbon group of from 1 to about 20 carbon atoms; R² is an alkyl group of from 1 to about 5 carbon atoms; R³ is phenyl or an alkyl group of from 1 to about 8 carbon atoms; G is a monovalent or polyvalent hydrocarbon group of from 1 to about 30 carbon atoms or a heterocarbon group of from 1 to about 30 carbon atoms containing one or more heteroatoms; subscript a is 0, 1 or 2; and, subscript x is 1, 2, 3 or
 4. 3. The method of claim 1, wherein the imino-functional silane is at least one member selected from the group consisting of: aldimino-functional silane of general formula (IV):

wherein: R¹ is a divalent hydrocarbon group of up to about 20 carbon atoms or a divalent heterocarbon group of up to about 20 carbon atoms containing one or more heteroatoms; R² is an alkyl group of from 1 to about 5 carbon atoms; R³ is phenyl or an alkyl group of from 1 to about 8 carbon atoms; Y¹ and Y² each independently is hydrogen, an organic radical or together with the carbon atom to which they are bonded form a carbocyclic or heterocyclic ring of from about 5 to about 8 ring atoms; Y³ is hydrogen, an unsubstituted or substituted alkyl group of up to about 10 carbon atoms containing one or more heteroatoms, an unbranched or branched alkyl or alkylenyl group of up to about 10 carbon atoms, a substituted or unsubstituted aryl or arylalkyl group of up to about 20 carbon atoms, or an —OR⁴, —OC(═O)—R⁴, —C(═O)OR⁴ or —C(═O)R⁴ group in which R⁴ is an unsubstituted or substituted alkyl group of from 3 to about 20 carbon atoms; and, subscript a is 0, 1 or 2, aldimino-functional silane of general formula (VI):

wherein: R¹, R², R³ and subscript a have the aforestated meanings for aldimino-functional silane (IV); R⁵ and R⁶ each independently is hydrogen, a monovalent hydrocarbon group of from 1 to about 12 carbon atoms or together with the carbon atom to which they are bonded form an unsubstituted or substituted ring of from about 5 to about 12 carbon atoms, or a heterocarbon group containing from 1 to about 12 carbon atoms; R⁷ is hydrogen, a monovalent hydrocarbon group of up to about 20 carbon atoms, a heterocarbon group containing up to about 20 carbon atoms and one or more heteroatoms, or an alkoxycarboxyl group of from 2 to about 20 carbon atoms; and, R⁸ and R⁹ each independently is a monovalent hydrocarbon group of up to about 20 carbon atoms, a heterocarbon group containing up to about 20 carbon atoms and one or more heteroatoms, or an alkoxycarboxyl group of from 2 to about 20 carbon atoms, or R⁸ and R⁹ and the carbon atom to which they are bonded form an unsubstituted or substituted ring of from about 5 to about 12 carbon atoms containing zero, one or more heteroatoms, and ketimino-functional silane of general formula (VIII):

wherein: R¹, R², R³ and subscript a each have one of the same meanings stated above for aldimino-functional silane (IV); R¹⁰ and R¹¹ each independently is a monovalent hydrocarbon group of up to about 20 carbon atoms or a monovalent heterocarbon group of up to about 20 carbon atoms containing one or more heteroatoms; and, subscript a is 0, 1 or
 2. 4. The method of claim 1, wherein the Brønsted-Lowry base is a compound having the general formula (X): M(OR)_(f)   (X) wherein M is an alkali metal or alkaline earth metal and R is hydrogen, a hydrocarbon group of from 1 to about 20 carbon atoms, a heterocarbon group of up to about 20 carbon atoms, specifically from 1 to about 12 carbon atoms and still more specifically from 1 to about 6 carbon atoms, a p-orbital of the oxygen atom containing a lone paired electrons, or M, and subscript f is 1 or 2, with the provisos that (i) when M is an alkali metal, then subscript f is 1; (ii) when M is an alkaline earth metal, then subscript f is 2, except when R is a p-orbital of oxygen atom containing a lone pair of electrons; (iii) when R is M, then M is an alkali metal; and (iv) when R is a p-orbital of the oxygen atom containing a lone pair of electrons, then M is an alkaline metal and subscript f is
 1. It is understood that the Brønsted-Lowry base of formula (X) is a salt of an alkali or alkaline hydroxide, alkoxide or oxide.
 5. The method of claim 4, wherein in Brønsted-Lowry base (X), M is an alkali or alkaline earth metal, R is hydrogen or a hydrocarbon group of from 1 to about 20 carbon atoms and subscript f is 1 or 2, with the provisos that when M is an alkali metal, subscript f is 1 and when M is an alkaline earth metal, subscript f is
 2. 6. The method of claim 1, wherein the Brønsted-Lowry base is at least one member selected from the group consisting of alkali metal and alkaline metal hydroxides, alkoxides and oxides.
 7. The method of claim 1, wherein the Brønsted-Lowry base is at least one member selected from the group consisting of LiOH, NaOH, KOH, CsOH, Mg(OH)₂, Ca(OH)₂, Ba(OH)₂, NaOMe, KOMe, NaOEt, KOEt, CaO, MgO and BaO.
 8. The method of claim 1, wherein the amount of Brønsted-Lowry base (X) added to the imino-functional silane ranges from about 0.0001 to about 10 weight percent based upon the total weight of the imino-functional silane and Brønsted-Lowry base.
 9. The method of claim 1, wherein the Brønsted-Lowry base is soluble in the imino-functional silane at the concentration employed and matches the alkoxy functionality of the silane moiety of the imino-functional silane.
 10. The method of claim 1, wherein the stabilized imino-functional silane is an imino-functional silane containing less than about 2 weight percent conjugated carbon-carbon double bond-containing imino-functional silane based on the total weight of conjugated carbon-carbon double bond-containing imino-functional silane and imino-functional silane when stored at 25° C. for 4 weeks.
 11. The method of claim 1, wherein the stabilized imino-functional silane contains from about 0.0001 to about 0.1 weight percent of Brønsted-Lowry base based on the weight of the imino-functional silane.
 12. The method of claim 1, wherein the method further comprises neutralizing a proton source in the mixture from step (b) with at least one Brønsted-Lowry base.
 13. The method of claim 1 further comprising separating the at least one Brønsted-Lowry base from the mixture of imino-functional silane with the at least one Brønsted-Lowry base after the proton source in the mixture of step (b) has been neutralized with the at least one Brønsted-Lowry base.
 14. The method of claim 13, wherein the step of separating is at least one of distilling the mixture of the imino-functional silane and the at least one Brønsted-Lowry base, passing such mixture through an ion exchange resin, extracting such mixture, and applying a preparatory chromatographic method to such mixture.
 15. The method of claim 1, wherein the imino-functional silane is (1,3-dimethyl-butylidene)-(3-triethoxy-silanyl-propyl)-amine, (1,3-dimethyl-butylidene)-(3-trimethoxy-silanyl-propyl)-amine, (1,3-dimethyl-butylidene)-(2,2-dimethyl-4-triethoxysilanyl-butyl)-amine, isopropylidene-(3-methyl-diethoxy-silanyl-propyl)-amine, sec-butylidene-(3-triethoxy-silanyl-propyl)-amine, [3-(triethoxy-silanyl)-propyl]-(1-phenyl-ethylidene)-amine, ethylidene-(3-dimethyl-ethoxy-silanyl-propyl)-amine, (3-methyl-butylidene)-(3-triethoxy-silanyl-propyl)-amine, benzylidene-(3-triethoxy-silanyl-propyl)-amine, [2,2-dimethyl-3-(3-triethoxy-silanyl-propylimino)-propyl]-dimethyl-amine, N-sec-butylidene-N′-(3-trimethoxy-silanyl-propyl)-ethane-1,2-diamine or 3-(1-octylidene aminopropyltrimetheoxysilane.
 16. The method of claim 1, wherein in step (a), the imino-functional silane is susceptible to undergoing self-addition and deamination reactions resulting from the presence therein of a proton source and in step (b) the Brønsted-Lowry base neutralizes the proton source thereby inhibiting such self-addition and deamination reactions.
 17. The method of claim 1, which further comprises: c) separating the Brønsted-Lowry base from the stabilized imino-functional silane; and, d) collecting the stabilized imino-functional silane from step (c).
 18. The method of claim 16, which further comprises: c) separating the Brønsted-Lowry base from the stabilized imino-functional silane; and, d) collecting the stabilized imino-functional silane from step (c).
 19. The method of claim 17, wherein separating step (c) is carried out by at least one of distilling the mixture of the imino-functional silane and the at least one Brønsted-Lowry base, and passing such mixture through an ion exchange resin or membrane.
 20. The method of claim 18, wherein separating step (c) is carried out by at least one of distilling the mixture of the imino-functional silane and the at least one Brønsted-Lowry base, and passing such mixture through an ion exchange resin or membrane.
 21. The method of claim 16, wherein the amount of Brønsted-Lowry base added to the imino-functional silane is sufficient to inhibit self-addition and deamination reactions of the imino-functional silane.
 22. The method of claim 16 wherein the amount of Brønsted-Lowry base added to the imino-functional silane is at least 1 molar equivalent based on the moles of proton source present in the imino-functional silane.
 23. A stabilized imino-functional silane substantially free of a proton source and containing less than about 2 weight percent conjugated carbon-carbon double bond-containing imino-functional silane based on the total weight of conjugated carbon-carbon double bond-containing imino-functional silane and imino-functional silane.
 24. A stabilized imino-functional silane substantially free of a proton source and containing less than about 0.5 weight percent conjugated carbon-carbon double bond-containing imino-functional silane based on the total weight of conjugated carbon-carbon double bond-containing imino-functional silane and imino-functional silane.
 25. The stabilized imino-functional silane of claim 23 containing less than about 15 ppm proton source based on the weight of the imino-functional silane.
 26. The stabilized imino-functional silane of claim 23 containing less than about 1 ppm proton source based on the weight of the imino-functional silane.
 27. The stabilized imino-functional silane of claim 23 containing less than about 0.5 weight percent conjugated carbon-carbon double bond-containing imino-functional silane based on the total weight of conjugated carbon-carbon double bond-containing imino-functional silane and containing less than about 15 ppm proton source based on the weight of the imino-functional silane.
 28. The stabilized imino-functional silane of claim 23 containing less than about 0.1 weight percent conjugated carbon-carbon double bond-containing imino-functional silane based on the total weight of conjugated carbon-carbon double bond-containing imino-functional silane and containing less than about 1 ppm proton source based on the weight of the imino-functional silane. 